Such a baby bottle comprising a bottle jacket open on both sides thereof is already known from U.S. Pat. No. 5,499,729 A. There, a baby bottle consisting of a cylindrical jacket is disclosed, wherein a sleeve cap is screwed to the open end thereof for fastening a teat. In the oppositely arranged bottom region, a further cap is provided for clamping engagement of a diaphragm as an elastomeric valve element. The diaphragm has a plurality of apertures which, in the relaxed state of the diaphragm, are in their closed positions. When applying a negative pressure in the container interior, the apertures are cleared for the passage of air. There, the bottom region of the baby bottle is relatively small, so that also the valve element arranged in the bottom region has only a comparatively small area. The cylindrical jacket consists of a polycarbonate material common with baby bottles which is blow-molded.
Furthermore, a bottle jacket, in particular for baby bottles, having two open ends is known from U.S. Pat. No. 6,142,325 A, wherein a bottom cap having a valve element is screwed to a bottom-side end portion. However, also here a comparatively small bottom area and, thus, only a relatively small valve element is provided so that an entry of air into the interior of the baby bottle is possible only in case of relatively large pressure differences. The bottle jacket may be made of glass, polyester, polyamides, polyolefins, polycarbonates and the like.
From U.S. Pat. No. 6,053,342 A, a baby bottle is known in which a cylindrical, angled bottle jacket open on both sides thereof is provided. Here, too, a teat is fastened to an end region by means of a sleeve cap, and in the relatively small opposite bottom region a cap with an elastic diaphragm having air passage openings is provided, the diaphragm being connected to the cap via at least one tab. The bottle jacket which is open on both sides is produced from polycarbonate by a blow molding method.
From FR 647 873 A, still another baby bottle is known which includes a special drinking spout molded in one piece with the bottle jacket. This special bottle jacket which may have a conical shape is open on its bottom side, a fastening ring which carries a bottom surface being screwed to the open end portion. In order to prevent corrosion, this bottom surface preferably is made of aluminum.
From U.S. Pat. No. 4,613,050 A, yet another baby bottle having a conventional cup-shaped bottle jacket is known, a special air valve being provided in the region of the screw cap so as to enable an intake of air into the baby bottle.
So far, food intake by babies from such baby bottles has been markedly different from drinking at a mother's breast. At the mother's breast, the extremely soft nipple is almost exclusively stripped by the baby's tongue and palate, and since this does not cause any negative pressure (vacuum) in the mother's breast, completely steady drinking is possible. In particular, no or only slight sucking (vacuum) is used by the baby him/herself in order to get the milk into his/her mouth and then swallow the former. Drinking practically corresponds to drinking from a cup, accompanied by additional stripping.
In the known baby bottles, however, a negative pressure forms in the bottle already with the first drinking, which the baby counteracts by producing a stronger vacuum (sucking). This type of sucking will then have the effect that also air is sucked in and swallowed from the mouth cavity. This air will then give rise to the highly uncomfortable colics which are extremely stressful for mother and child and from which many babies suffer seriously. Moreover, the sucking portion must be comparatively stiff and hard so that it will not collapse, as a consequence of the negative pressure prevailing in the bottle, and thereby render drinking impossible. Yet, such a stiff sucking part practically does not allow any stripping, whereby the child gets at the milk—and also at the undesired air—practically only by sucking (vacuum).